Lancets

ABSTRACT

A lancet has a generally tubular body ( 1 ). A hollow insert ( 4 ) with a closed end plugs one end of the body ( 1 ), and it has a co-axial projection ( 5 ) forming a sharp tip proud of that end of the body. The body ( 1 ) and insert ( 4 ) are simultaneously formed by twin shot moulding, the body being of polyethylene and the insert being of a liquid crystal polymer which will create a sharp tip of adequate strength.

This is a 371 National Stage application of International applicationno. PCT/GB03/00473, filed Feb. 5, 2003, which claims priority to GreatBritain application no. 0202603.7, filed Feb. 5, 2002. The entirecontents of the above-referenced applications are hereby incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

This invention relates to lancets for skin prickers, used to draw a dropof blood for analysis.

The conventional construction of such a lancet is a steel needle encasedalmost entirely in an elongate plastics body but with its sharp tipprojecting from one end. The plastics body eases handling and can beshaped to be guided by a compatible firing device and to locate one endof a spring which shoots the lancet forwards when released. It is alsoquite usual to have the needle tip encased in a twist-off cap integrallymoulded with the plastics body. This keeps the tip safe and clean untilimmediately before use.

One problem with steel needles is that they are generally straightcylindrical bodies, apart from their tips, and they may be siliconised.Therefore the plastics of the body can have very little frictional gripon the needle that it encases, and it is not unknown for the needle tobe shifted forwards relative to the body when the cap is twisted andpulled. This results in too deep a prick when the lancet is fired.

The manufacture of such a lancet necessarily involves more than onestep. The steel needle has to be made first, and this in itself meanstaking a blank and then grinding or otherwise sharpening one end tocreate the tip. Then the needle is located in a mould, and finally isencased in the plastics body. It would clearly be advantageous to reducethe number of operations and form the needle tip with the body. However,an all-steel lancet would be far too extravagant, if nothing else sincelancets are disposable, single use items, while simply moulding the bodyto have a tip at one end of the same material as the plastics body willnot produce a sharp enough point if the usual plastics (polyethylene) isemployed.

It is the aim of this invention to overcome, at least in part, thesedrawbacks.

SUMMARY OF THE INVENTION

According to the present invention there is provided a lancet for skinpricking, the lancet comprising an elongate plastics body with aplastics insert affixed at one end providing a sharp tip projecting fromthat end, the plastics material of the insert being a liquid crystalpolymer.

Such a liquid crystal polymer, when melted, has extremely low viscosityand can-flow almost like water. It can therefore penetrate fully intothe part of a mould cavity which will form the needle tip. Moreover itsstrength when set in the direction of flow is very high. Therefore theinsert emerges from the mould with the tip sharp and ready for use.

Liquid crystal polymers are expensive, and so the body of the lancetwill be of less costly material and polyethylene can continue to beused.

The body and the insert can be formed together in a single process bytwin-shot moulding.

In the preferred form the body is generally tubular, the insert pluggingone end. This enables the spring of a firing device to enter the other,open end of the body and to act directly on the insert, the body thenserving primarily as guide member. Because the spring would not then acton the rear end of the body, this could enable the firing device to bemore compact than existing ones.

A further advantage of the all-plastics construction is that suchlancets will be easier to dispose of completely by incineration: therewill be no steel needles to melt down or burn away.

While many firing devices automatically retract lancets to make themsafe after use, this all-plastics lancet can quite easily be made saferto some degree if the tip is exposed. By pressing the tip at an angleagainst a hard surface the extremity can be broken off, leaving ablunted stump.

For a better understanding of the invention one embodiment will now bedescribed, by way of example, with reference to the accompanyingdrawing, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an all-plastics lancet of the invention;

FIG. 2 is a side view at 90° to that of FIG. 1; and

FIG. 3 is a cross-section through the lancet shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The lancet has a generally tubular body 1 with four evenly spacedexternal longitudinal fins 2. Two opposed ones are interrupted at theirmid-length by apertures 3 through the body 1, left as part of themoulding process.

A hollow insert 4 with a closed end plugs one end of the body 1, and ithas a co-axial projection 5 forming an integral sharp tip proud of thatend of the body. A cylindrical rear portion of insert 4 includes arear-facing edge 8 abutting an interior shoulder 7 within the body 1.The forward end of the body 1 is closed by an end wall 10. The insert 4and the body 1 together can define a contiguous or uninterrupted tubularpassage 9.

The insert 4 is moulded first as a monolithic structure, then the body 1is moulded over the insert 4 during a twin-shot moulding process,forming a twist-off cap 6 which provides a sterile shield surroundingand protecting the needle tip 5. The body is formed from a low costrelatively soft material such as polyethylene, whilst the insert isformed from a liquid crystal polymer.

1. A lancet for skin pricking, comprising: an elongate tubular plasticbody of a first plastic material, the body having a forward end and arearward end, and an interior surface defining a first tubular region;and a hollow plastic insert of a second plastic material, the firstplastic material being different from the second plastic material, theplastic insert being molded to form a monolithic structure comprising asecond tubular region that defines a hollow cylindrical rear portion, aclosed forward end, and an integral sharp tip at the closed forward end,the plastic insert located within the body and with the integral sharptip projecting through said forward end of the body, the body beingmolded over the insert such that: the forward end of the body is closedby an end wall, with the sharp tip of said insert projecting from aforward surface of the end wall, and a rear surface of the end wallabuts the closed forward end of the insert, blocking forward movement ofthe insert relative to the body; and the body forms an interior shoulderwithin the first tubular region which abuts the cylindrical rear portionof the insert, blocking rearward movement of the insert relative to thebody, thereby affixing the insert within the body, wherein, the plasticinsert is immovable relative to the body, the second plastic materialforming the plastic insert is a liquid crystal polymer, and the firsttubular region and the second tubular region together define a tubularpassage closed at said forward end.
 2. The lancet according to claim 1,wherein the first plastic material comprises polyethylene.
 3. The lancetaccording to claim 1, wherein the body and the plastics insert have beenformed together in a single operation by twin-shot moulding.
 4. Thelancet according to claim 1, wherein the body further comprises externalfins extending longitudinally on an external surface of the body.
 5. Thelancet according to claim 1, further comprising a twist-off cap integralwith the body and covering the sharp tip.
 6. The lancet according toclaim 1, wherein the first tubular region and the second tubular regiontogether define a contiguous tubular passage.
 7. The lancet according toclaim 1, wherein the first tubular region and the second tubular regiontogether define an uninterrupted tubular passage.
 8. A lancet for skinpricking, comprising: an elongate tubular plastic body, the body havinga forward end and a rearward end, and an interior surface defining afirst tubular region; and a hollow liquid crystal polymer insert, thepolymer insert being a monolithic structure comprising a second tubularregion and a closed forward end providing an integral sharp tip, theinsert being located within the body, with an outer surface of theinsert contacting an inner surface of the forward end of the body,blocking forward movement of the insert relative to the body, and withthe integral sharp tip projecting through said forward end of the body,and an outer surface of a rearward end of the insert contacting aninterior shoulder of the body, blocking rearward movement of the insertrelative to the body, wherein the first tubular region and the secondtubular region together define a tubular passage closed at said forwardend, and the insert is immovable relative to the body.
 9. The lancetaccording to claim 8, wherein the body is formed from polyethylene. 10.The lancet according to claim 8, wherein the body further comprisesexternal fins extending longitudinally on an exterior surface of thebody.
 11. The lancet according to claim 8, further comprising atwist-off cap integral with the body and covering the sharp tip.
 12. Thelancet according to claim 8, wherein said second tubular region definesa hollow cylindrical rear portion of said insert.
 13. The lancetaccording to claim 12, wherein said hollow cylindrical rear portion isclosed at a forward end by a planar end wall, and the end wall comprisesa forward surface through which projects said sharp tip.
 14. The lancetaccording to claim 12, wherein, said body comprises an interior shoulderwithin said first tubular region, and said cylindrical rear portion ofsaid insert comprises a rear-facing edge abutting the shoulder of saidbody blocking rearward movement of the plastic insert relative to thebody.
 15. A lancet for skin pricking, comprising: an elongate tubularplastic body, the body having a closed forward end and an open rearwardend, and an interior first tubular region; and a plastic insert, theinsert being a monolithic structure comprising a second tubular regionand a closed forward end providing an integral sharp tip, the insertbeing located within the body with an outer surface of the insertcontacting an inner surface of the body, blocking forward movement ofthe insert relative to the body, and an outer surface of the insertcontacting an interior shoulder of the body, blocking rearward movementof the insert relative to the body, the insert thus being immovablerelative to the body, with the integral sharp tip projecting throughsaid forward end of the body, and with the first tubular region and thesecond tubular region together defining a tubular passage closed at saidforward end and open at said rearward end.
 16. A lancet for skinpricking, comprising: an elongate tubular plastic body of a firstplastic material, the body having a forward end and a rearward end, andan interior surface defining a first tubular region; and a plasticinsert consisting of a second plastic material comprising liquid crystalpolymer, the second plastic material being different from the firstplastic material, the insert being a monolithic structure comprising: asecond tubular region, a closed forward end, and an integral sharp tip,the first tubular region of the body and the second tubular region ofthe insert together defining a tubular passage closed at the forwardend, the lancet being formed by a molding process comprising firstmolding the insert as a monolithic structure and then molding the bodyover the insert, the molding process being such that the forward end ofthe body is closed by an end wall, the sharp tip projecting through aforward surface of the end wall and a rear surface of the end wallabutting the closed forward end of the insert, blocking forward movementof the insert relative to the body, and being such that the body formsan interior shoulder within the first tubular region and abutting thecylindrical rear portion of the insert, blocking rearward movement ofthe insert relative to the body, thereby permanently affixing the insertrelative to the body.